Resolve BeamDyn initial strain for rotated blade #1796
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In the BeamDyn driver, and likely in the glue-code, if the blade was initially rotated then an initial strain was introduced which produced forces when no loads or gravity had been applied. The cause was traced to the calculation of R0 (initial rotation) at the quadrature points which was interpolated via the shape functions from the element nodal rotations. The shape function interpolation is not exact and introduced strains on the order of 1e-7, but with the large stiffness of the blade, forces of 6200 N could be produced at the root for the IEA 15MW blade. This was resolved by directly calculating the quadrature point initial rotations in uu0(4:6) via interpolated tangent and twist, which are well behaved. This was only a problem for non-straight blades such as the IEA 15MW. This commit also fixes a bug where the parameter UsePitchAct wasn't initialized from the input file until after it was used in SetOutParam. The initialization has been moved to SetParameters.
andrew-platt
approved these changes
Oct 6, 2023
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This pull request is ready to be merged. Copy of PR #1663 applied to the
rc-3.5.1branch.Feature or improvement description
In the BeamDyn driver, and likely in the glue-code, if the blade was initially rotated then an initial strain was introduced which produced forces when no loads or gravity had been applied. The cause was traced to the calculation of R0 (initial rotation) at the quadrature points which was interpolated via the shape functions from the element nodal rotations. The shape function interpolation is not exact and introduced strains on the order of 1e-7, but with the large stiffness of the blade, forces of 6200 N could be produced at the root for the IEA 15MW blade. This was resolved by directly calculating the quadrature point initial rotations in uu0(4:6) via interpolated tangent and twist, which are well behaved. This was only a problem for non-straight blades such as the IEA 15MW.
This commit also fixes a bug where the parameter UsePitchAct wasn't initialized from the input file until after it was used in SetOutParam. The initialization has been moved to SetParameters.
Related issue, if one exists
This changes resolves Issue #366 when QuasiStaticInit is set to False.
Impacted areas of the software
BeamDyn
Test results, if applicable
The BeamDyn unit test test_BD_QuadraturePointData.F90 was updated to account for the slight difference in R0, E1, Stiffness that resulted from this change.